1. Field of the Invention
This invention relates generally to the field of packaging, and more specifically to the field of hot fill type containers.
2. Description of the Related Technology
Hot fill containers are designed to be used with the conventional hot fill process in which a liquid product such as fruit juice is introduced into the container while warm or hot, as appropriate, for sanitary packaging of the product.
After filling, such containers undergo significant volumetric shrinkage as a result of the cooling of the product within the sealed container. Hot fill type containers accordingly must be designed to have the capability of accommodating such shrinkage. Typically this has been done by incorporating one or more concave vacuum panels into the side wall of the container that are designed to flex inwardly as the volume of the product within the container decreases as a result of cooling.
Most hot fill type containers are fabricated from polyethylene terephthalate, which is otherwise known as PET. PET possesses excellent characteristics for such containers, but PET resin is relatively expensive. Accordingly, a PET container design that reduces the amount of material that is used without sacrificing performance will provide a significant competitive advantage within the packaging industry.
Hot fill containers must be designed to be strong enough in the areas outside of the vacuum panel regions so that the deformation that occurs as a result of the volumetric shrinkage of a product within the container is substantially limited to the portions of the container that are designed specifically to accommodate such shrinkage. In order to provide the requisite strength, the wall thickness of the side wall of the container must be formed to a minimum thickness.
Typically, the vacuum panel regions of conventional hot fill containers are characterized by having surfaces that are designed to deflect inwardly when the product within the sealed container undergoes shrinkage. In some instances, an island may be defined in the middle of the vacuum panel in order to provide support for in order to provide support for an adhesive label that may be placed over the container. In other instances, such as is disclosed in U.S. Pat. No. 5,472,105 to Krishnakumar et al., ribs may be molded into the vacuum panel area in order to provide an enhanced grip surface or to enhance the strength of the vacuum panel area. While such designs improve the functionality of certain containers to some extent, they had little to no effect on the volumetric efficiency of the vacuum panel, i.e. the amount of volumetric shrinkage that could be accommodated by a given amount of inward deflection of a vacuum panel having given dimensions.
A need has existed for an improved hot fill container design that possesses improved volumetric efficiency characteristics and that may permit substantial lightweighting of the container without sacrificing container performance.